#include <stdio.h>		/* 				DISP98.C	*/
#include <starbase.c.h>

#define TOP	 40
#define BOTTOM	760
#define WIDTH   720
#define Y_OFF   400
#define X0       20
#define X100   1023

static	int	gfd, holdit;
static	int	drawbuf[(X100-X0+1)*2];
static	int	drawmax = (X100-X0 +1);
static  char	caption[100];

dsplRgraph(fstart,npts,msg)		/* called from display.c */
 float  *fstart;
 int	npts;
 char	*msg;
{ 
	 register float *fp;			/* ptr to src array */
	 register int   *dbp;			/* ptr to drawbuf */
	 register int   xord, xinc, xend, finc;
	 int	drawpts;
	 float	max, min, absmax, fscale, *fplim;

	 if (!gfd)				/* open display once */
	   gfdopen();
	 if (npts <= drawmax) {			/* for this npts in,	*/
		  finc = 1;			/*   set incrs for simple */
		  xinc = drawmax/npts;		/*   mapping onto drawmax */
		  xend = X0 + xinc*(npts-1);
	 }
 	 else {
		  finc = (npts-1)/drawmax + 1;
		  xinc = 1;
		  xend = X0 + npts/finc -1;
	 }
 	 for (fp=fstart, fplim=fstart+npts, max=0, min=0; fp<fplim; fp++ ) {
		  if (*fp > max)
		    max = *fp;
		  else if (*fp < min)		/* determine maxamp	*/
		    min = *fp;			/*   for scaling	*/
	 }
 	 if (max >= -min)
	   absmax = max;
	 else absmax = -min;
	 fscale = (WIDTH>>1) / absmax;
	 for (fp=fstart, dbp=drawbuf, xord=X0; xord <= xend; xord += xinc ) {
		  *dbp++ = xord;		/* scale into drawbuf  */
		  *dbp++ = Y_OFF - (int)(*fp * fscale);
		  fp += finc;
	 }
 	 drawpts = (dbp - drawbuf) >> 1;	/* and prepare caption	*/
	 sprintf(caption, "%s  %d points, scalemax %8.2f", msg, npts, absmax);
	 while(holdit)
	   ;				    	/* if we wish to proceed, */
 	 dcrectangle(gfd, X0,0, X100,BOTTOM);	/*  erase screen for redraw */
	 line_color_index(gfd, 2);			/* red */
 	 dcmove(gfd, X0, Y_OFF);			/* draw x-axis */
 	 dcdraw(gfd, xend, Y_OFF);
 	 line_color_index(gfd, 1);			/* white */
         dcpolyline(gfd, drawbuf, drawpts, FALSE);	/* draw segment */
	 dctext(gfd, X0, TOP-10, caption);		/*  and caption */
}


gfdopen()
{
	 int y, yinc, yy, yyinc;

	 gfd = gopen("/dev/graphics",OUTDEV,"hp98710",INIT); 
 	 buffer_mode(gfd,0);				/* open graphics */
	 mapping_mode (gfd,1);				/* set params */
	 system("linear 128 255 0 0 0");
	 fill_color_index(gfd, 128);
	 perimeter_color_index(gfd, 128);
	 dcrectangle(gfd, X0,0, X100,TOP-1);
	 dcrectangle(gfd, X0,BOTTOM+1, X100,768);
	 fill_color_index(gfd,0);
	 perimeter_color_index(gfd, 0);
	 line_color_index(gfd, 2);
	 dcmove(gfd, X0-1, TOP);			/* draw y-axis */
	 dcdraw(gfd, X0-1, BOTTOM);
	 yinc = WIDTH/4;
	 yyinc = yinc/5;
	 for (y = TOP; y <= BOTTOM; ) {			/*  and hatch marks */
		  dcmove(gfd, X0-12, y);
		  dcdraw(gfd, X0-1, y);
		  yy = y;
		  y += yinc;
		  while ((yy += yyinc) < y && yy < BOTTOM) {
			   dcmove(gfd, X0-6, yy);
			   dcdraw(gfd, X0-1, yy);
		  }
	 }
 }